The field of tissue engineering explores the ways in which cell culture technology can be combined with polymer technology to generate new tissues of predesigned shape and volume (see Principles of Tissue Engineering, Second Edition, Lanza et al., Eds., Academic Press, 2000). The field is largely grounded in the idea that biological tissues can be generated or repaired through the application and control of cells, synthetic materials, and chemo-attractive proteins (reviewed in Bonassar and Vacanti, J. of Cell. Biochem. Supp., 30/31: 297-303, 1998). Tissue engineering technology offers the promise of tissue regeneration and replacement following trauma or a variety of diseases or birth defects. It can also be used in the context of cosmetic procedures.
Both autologous and heterologous tissue or cells can be made in tissue engineering techniques. The use of autologous tissue in tissue engineering provides advantages in that it helps to reduce the risk that the engineered tissues will provoke an immune response. In some instances, when creating an autologous implant, donor tissue is harvested and dissociated into individual cells, and the cells are attached and cultured on a substrate that is implanted at the desired site of the functioning tissue. Many isolated cell types can be expanded in vitro using cell culture techniques. However, primary organ cells, which are often in demand in tissue engineering, are generally believed to be anchorage dependent and to require specific environments, often including the presence of a supporting material, or scaffold, to act as a template for growth. Current tissue engineering technology provides an artificial extracellular matrix for cell culture. Since successful cell transplantation therapy depends on the development of suitable substrates for both in vitro and in vivo tissue culture, the development of an extracellular matrix that contains natural materials and that is suitable for implantation would have more of the characteristics of the endogenous tissue. This is an ongoing challenge in the field of tissue engineering (see Yang et al., Tissue Engineering 7:679-689, 2001).